A variety of cyclonic combustion apparatuses of the general type described herein have been proposed in the past. Such apparatuses generate unacceptable amounts of nitrogen oxides (NO.sub.x), especially thermal nitrogen oxides, during combustion. It is believed that such apparatuses have not, therefore, been put into actual use, at least in Japan.
The present invention is based upon a determination that the construction of the combustion chamber is an important factor in the failure of conventional cyclonic type combustion apparatuses to reduce nitrogen oxide generation. In prior art cyclonic type combustion apparatuses, the walls of the combustion chambers are generally made of refractory materials. In such apparatuses, the flame temperature rises, and they fail in practice to reduce nitrogen oxide generation very much.